[Ardour-Users] export format profile

Anahata anahata at treewind.co.uk
Thu Feb 28 02:17:25 PST 2019

On Wed, Feb 27, 2019 at 08:13:28PM -0800, I. Ivanov wrote:
> I am struggling to understand the "*Dithering*" setting. Can you advice
> please what is the difference between the 4 options "Shaped Noise",
> "Triangular", "Rectangular" and "None"?

They are different ways of adding a small amont of random noise to make sure 
the quantization errors are random and not signal dependent.

Rectangular adds a maximum of 1lsb amplitude random noise, with a flat
amplitude distribution over the range -0.5lsb to +0.5lsb. That's the
minimum possible, but the level of the perceived noise (if you can hear
it at all) is not constant.

Triangular adds noise of twice that peak amplitude, with with a
trangular probability distribution, i.e. small values occur more
frequently than large values. The effective noise level at the output is
then constant, which is is arguably less objectionable (again, if you
can hear it at all)

Shaped noise alters the spectrum of the random noise to de-emphasise
frequencies at which the ear is most sensitive (around 3 kHz) with a
corresponding higher amplitude at high and low frequencies. The result
lowers the perceived level of the added noise (again, if you can hear it
at all)

Some people argue that at 16 bits dynamic range the quantization noise is 
so low that you can't hear it anyway, so dithering is unnecessary. I
don't recommend "none", because on very high dynamic range material,
some people can hear the difference (typically quiet reverb tails or
string instrument note decays not being smooth)

I usually choose "triangular", for what it's worth.

Full and very detailed explanation on this YouTube video

(go the the beginning or watch the part 1 video too if you need more
background. Also there's another video with audible examples, which I
can't currently find)

anahata at treewind.co.uk -+- http://www.treewind.co.uk
Home: 01535 501017         Mob: 07976 263827

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